Lesson 14 Flashcards
What are the 4 different componets to a transducer?
- Lens
- Matching layer
- Single crystal element
- Backing material
- damping
What are elements?
Crystals
What happens to beam profiles in transducers?
They go in and out at the same time
- no pulses
What is happening to beam width in pulse waves?
They are changing
- naturally shortens and widens again
Where is the natural focus on a pulse wave beam profile?
At the smallest point
Where is the near zone?
Between the focus point and the transducer
- minimun beam width
Where is the far zone?
From the focus point and onwards
What are 2 other names for the near zone?
- Fresnel zone
2. Near field
What happens to the beam width when increasing distance from the transducer in the near field?
It decreases
Beam convergence
Light rays comes together (converges) after reflection and refraction at a single point known as the focus
What are 2 other names for far zone?
- Fraunhofer zone
2. Far field
What happens to the bandwidth with increasing distance from the transducer in the far-field?
It increases
Beam divergence
When beams of light move away from each other after passing the focus point and going into the far field
Aperture
For a single disk transducer, this is the element size or width of group of elements
- opening
- top by the transducer
What does beam width change with?
Depth
What does beam width affect? (2)
- Resolution of signal at that depth
2. Intensity of the sound beam at that depth
What happens to the resolution with a more narrow beam width?
It gets better
When is intensity the strongest?
At a smaller focus point
What is considered to be uniform?
Power
- equal at any point along the beam
What is the formula for beam width (Wb) at the focus?
1/2 the aperture size
NZL
Near zone length
What is NZL determined by? (2)
- Size of the element
- aperture - Operating frequency
What happens to NZL if aperture increases?
It increases
What happens to NZL if frequency increases?
It increases
